1. Field of the Invention
The present invention relates to an optical pickup apparatus, and, more particularly, to a miniature optical pickup apparatus which is modularized so that an objective lens and an optical system move in a body. The present invention is effective in a drive apparatus in which the working distance between an optical pickup actuator and a media disc, which is a recording medium, is maintained to be not more than 0.5 mm, which is considerably smaller than the conventional working distance of 1 mm.
2. Description of the Related Art
A typical optical pickup apparatus used in optical disc drives such as CD players or DVD players includes a fixed unit having optical elements such as a laser diode and a photodiode, a mobile unit having an objective lens, and an actuator performing a control of an accurate position of the objective lens by adjusting the position of the mobile unit.
However, when the optical disc drive having the above structure is applied to portable appliances such as laptop computers or PDAs, a more compact structure is needed. Thus, the optical pickup is integrally modularized without separating the fixed unit and the mobile unit. The optical pickup is referred to as a miniature optical pickup apparatus.
FIGS. 1 and 2 show the structure of a conventional miniature optical pickup apparatus which is disclosed in PCT International Publication No. WO 02/29792 A2.
As shown in the drawings, an optical pickup apparatus 10 has a structure in which an optical pickup unit 12 is installed on one end portion of a swing arm 11. The swing arm 11 includes a first pivot 11a and a second pivot 11b. Thus, for the tracking control of the optical pickup unit 12, the swing arm 11 pivots left and right around the first pivot 11a while, for focusing control of the optical pickup unit 12, the one end of the swing arm 11 tilts up and down around the second pivot 11b. 
As shown in FIG. 2, the optical pickup unit 12 includes a laser diode 12a, an objective lens 12b focusing light on a recording surface of a disc D, and a photodetector 12c receiving light reflected by the disc D. Thus, the light emitted from the laser diode 12a passes along an inner optical path of the optical pickup unit 12 and focuses on the recording surface of the disc D through the objective lens 12b. The light reflected by the disc D passes along the inner optical path and arrives on the photodetector 12c. 
A heat sink plate 13 is coupled to the optical pickup unit 12 via a thermal conductive adhesive tape 14. The heat sink plate 13 dissipates heat generated from the optical pickup unit 12 during operation of the optical pickup apparatus 10. That is, when the laser diode 12a begins to emit light, heat is generated at the same time. If the heat is not properly dissipated, the laser diode 12a is overheated, and a malfunction is very likely to occur. Thus, the heat sink plate 13 performs a function of dissipating the heat transferred from the optical pickup unit 12 to the outside air.
Due to a trend of providing higher density in a recording medium such as an optical disc, increased optical power is required in an optical pickup apparatus. However, if a superior heat radiation efficiency is not provided in the higher powered optical pickup apparatus, the entire performance of a disk drive may be deteriorated. In the above-described conventional heat radiation structure, since the heat from the laser diode 12a is dissipated through the heat sink plate 13 only, the speed of heat radiation is slow, and a superior heat radiation efficiency cannot be expected. That is, assuming that the temperature at which the laser diode 12a is stably operated is about 80° C., when the laser diode 12a is overheated due to the heat radiation not being properly performed, the wavelength of the light is changed, and a malfunction may be generated. Also, since the threshold current of the laser diode 12a increases as the temperature increases, the amount of the heat generated increases, and the life span of the laser diode is shortened.
Therefore, a new heat radiation structure is needed which will result in a superior heat radiation efficiency.